Polystyrene (abbreviated as PS) is one of the five general-purpose synthetic resins, mainly including GPPS (general-purpose polystyrene), EPS (expandable polystyrene), and XPS (extruded expanded polystyrene). ), HIPS (impact polystyrene), PSX (cross-linked polystyrene), SAN (styrene-acrylonitrile copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), its output is only After PE (polyethylene), PVC (polyvinyl chloride) and PP (polypropylene), it ranks fourth. In 1925, the German I.G. Farben Industrial Company began to engage in the industrial production and development of styrene, and achieved industrial production in 1930 [1]. In 1958, China started the industrial production of PS resin [2]. It is estimated that global PS demand will reach 13.7 million tons in 2018, with an average annual growth rate (2013-2018) of 2.0 percentage points.
PS modified plastics are additives or other resins that use primary form of PS resin as the main component to improve the performance of the resin in one or more aspects such as mechanics, rheology, combustion, electricity, heat, light, magnetism, etc. As auxiliary ingredients, through filling, toughening, reinforcement, blending, reaction grafting, flame retardant, nanocomposite, functionalization, thermoplastic elastomer technology, alloying and other technical means, materials with uniform appearance and specific functions can be obtained.
PS is polymerized from styrene. According to the polymerization process, it can be divided into bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and isotactic polymerization. In particular, bulk polymerization and suspension polymerization are the most common. PS is one of the most widely used general plastics in the world. It has good dimensional stability and electrical insulation properties, excellent transparency, and its transparency is second only to PMMA (polymethyl methacrylate). Therefore, it has been widely used in the automotive and engineering industries, household appliances and other fields. However, due to its hardness and brittleness, poor impact resistance and low elongation at break (2%), it has been affected by its wide application in industry. Therefore, it needs to be modified. The modification of PS began with the research and development of HIPS by DOW Chemical Company in the United States in the early 1960s. In view of the shortcomings of GPS’s low toughness and notch sensitivity, a large number of physical, chemical and other modification research work have been carried out at home and abroad in order to improve the high impact strength of PS, improve its gloss and transparency, give it better performance and expand its application fields. .
1. Physical modification
Physical modification is mainly the blending of PO/PS, PE/PS, and the blending of PS with PC, ABS, PMMA, PPO, PVC, PA, K resin, reactive PS alloy, and other blends system etc.[3].
Li Huaidong et al. [4] used the method of increasing the screw speed of the twin-screw extruder during the material melt extrusion and blending process to study the mechanical shear stress and elastomer of the twin-screw extruder under higher screw speed conditions. The type, shape, dosage and other factors influence the mechanical properties and processing flow properties of ABS/PS blend materials. The results show that the high shear stress of the twin-screw extruder can promote the dispersion of dispersed phase particles and the enhancement of interfacial bonding force, resulting in an improvement in the mechanical properties and melt flow rate of the blend material. Nitrile rubber (NBR) powder has a compatibilizing and toughening effect on ABS/PS blend materials. When the extrusion blend temperature is 220 °C, the screw speed is 720 r/min, and the NBR powder mass fraction is 10%, ABS/PS The notched impact strength of the PS blend material is 16.4 kJ/m2, which is approximately 1.6 times higher than before modification, reaching the impact toughness index of ABS resin and maintaining good processing fluidity.
Li Chiyu[5] introduced the UPES resin developed by Nova Chemical Company in the United States. The new UPES resin is a mixture of PE and PS and can be used as a processing aid for LDPE (low-density polyethylene), HDPE (high-density polyethylene) and PP. agent. Its main function is to expand the processing range of polyolefins and directly improve the properties of some polyolefins.
Zhang Yu et al. [6] prepared PP/PS blends and reactive monomers styrene (St), acrylic acid (AA) and their mixed monomers to modify PP/PS blends, and used scanning electron microscopy to (SEM), polarized light microscopy (POM) and dynamic viscoelastic spectroscopy (DMA) were used to study the phase morphology and dynamic mechanical behavior of the reactive monomer modified PP/PS blend. The results show that the reactive monomer St has a compatibilizing effect, promotes the dispersion of PS in PP, and reduces the particle size of the dispersed phase PS. The reactive monomer AA has obvious heterogeneous nucleation effect, which reduces the spherulite size of PP. The compatibilization effect of St-modified blends is more obvious than that of AA-modified blends, while the heterogeneous nucleation effect of AA-modified blends is greater than that of St-modified blends.
Chen Gong et al. [7] modified PS with MAH (maleic anhydride) to increase the compatibility between PS and PA6, and then blended MAH-g-PS and PA6 in different proportions. The results show that when the mass fraction of MAH-g-PS is added to 0.5%, the impact strength of PA6/MAH-g-PS composites increases from 468 kJ/m2 to 700 kJ/m2 respectively. In addition, the flame retardant performance and combustion performance of its composite materials have been significantly improved.
Wang Genlin et al. [8] summarized the latest progress in the blending modification research of PVC and PS, mainly adding compatibilizer to the system for modification. It is hoped that the compatibilization-crosslinking synergistic technology can be used for blend modification of this system. The compatibilization-crosslinking synergistic technology has been used to modify blends of large varieties of general plastics, such as PVC/PE, PS/PE, etc., and has achieved good results. This technology is also being studied for the modification of PVC/PS blends.
Dai Xinying et al. [9] reviewed the research methods at home and abroad using graft copolymers, block copolymers and reactive blending to improve PS/PE compatibility, and proposed that PS/PO (polymer) should continue to be developed. olefins) alloys and convert them into industrial products.
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